Trinomial Nomenclature

Trinomial nomenclature (Latin tri, three) extends ordinary binomial nomenclature by adding a third name — generic name, species name and subspecies name — a system proposed by Thomas Henry Huxley and Hugh Edwin Strickland. It is used specifically when members of a species show large enough internal variation across their range or populations that the species can meaningfully be split into subspecies based on that variation.

Structurally, a trinomial name is simply the binomial system extended with a subspecies name added as the third word. All three names are italicised, but only the first (generic) name is capitalised, and a handwritten trinomial name should be underlined separately rather than continuously. The textbook's worked example is the Indian house crow, Corvus splendens splendens, where Corvus is the genus, the first splendens names the species, and the second splendens names the specific subspecies — letting taxonomists precisely ide …